1. Field of the Invention
The invention pertains to the field of optoelectronic systems carried on board aircraft, notably designed for the 3D localization and/or identification of targets, for example, and more particularly, to a self-retractable sighting device for a system such as this.
An major parameter in onboard optoelectronic systems for 3D localization and/or identification is the angular deflection of the line of sight. Indeed, it is quite important that this type of onboard equipment should enable localization and identification in the widest possible sectors. The ideal layout would be that in which the optoelectronic equipment is placed directly at the tip of the aircraft nose. This is generally not possible because of the presence of the radar at this position.
2. Description of the Prior Art
Positioning the optoelectronic equipment beneath the aircraft does not enable the line of sight to be oriented towards the elevation angles that are positive with respect to the horizontal fuselage reference of the aircraft.
A lateral positioning would present a big mask, in relative bearing, owing to the presence of the nose, unless two symmetrically positioned systems were used, thus notably increasing the cost.
The so-called "canopy base" layout, just before the windscreen, makes it possible to obtain the biggest acquisition fields and the most valuable ones from the operational point of view.
Now, the layout of an optoelectronic localization and acquisition equipment, notably in a warplane, in a canopy base layout creates a mask that is all the greater as the field of acquisition of the localizing equipment is big. To enable the orientation of the field, namely of the line of sight, downwards along elevation angles that are negative with respect to the horizontal fuselage reference HFR and are possibly big angles, the localizing system enabling the orientation of the line of sight should protrude out of the aircraft skin AS, as can be seen in FIG. 1 which shows an aircraft fuselage F in a partial view with its horizontal reference HFR. The pilot P in his cockpit has his bottom line of visibility BLV in the direction (in relative bearing) of the optoelectronic equipment limited by this system. The bottom line of sight Bls of the optoelectronic equipment is, for its part, limited by the fuselage or "skin" AS of the aircraft.
The main orientation devices of the line of sight mounted on presently existing aircraft do not generally enable a wide angular deflection of the line of sight, or else when the angular deflection is more or less suitable, the device blocks out the pilot's visibility to a major extent. These devices presently exist only on aircraft that are not subjected to the constraints necessitated by landings in extremely restricted zones, for example on aircraft carriers. Therefore, none of the devices existing to date is subjected to the constraints of visibility necessary for touchdown on an aircraft carrier.